Biology. Chapter 4. Cell Structure. Concepts and Applications 9e Starr Evers Starr

Transcription

1 Biology Concepts and Applications 9e Starr Evers Starr Chapter 4 Cell Structure 2015

2 4.1 What Is a Cell? Cell theory Prior to the invention of the microscope, the existence of cells was unknown Mid-1600s: Antoni van Leeuwenhoek constructed a crude microscope and observed animalcules These animalcules were in fact microbes

3 Cell Theory (cont d.) Components of the cell theory: All organisms consist of one or more cells, which are the basic unit of life All cells come from division of preexisting cells All cells pass hereditary material to offspring

4 Cell Theory (cont d.)

5 Components of All Cells All cells have at least three components in common: Plasma membrane Cytoplasm DNA

6 Components of All Cells (cont d.) DNA cytoplasm plasma membrane cytoplasm DNA in nucleus plasma membrane cytoplasm DNA in nucleus plasma membrane

7 Components of All Cells (cont d.) The plasma membrane is the outermost membrane of a cell The plasma membrane encloses a jellylike mixture called cytoplasm Suspended in the cytoplasm are specialized organelles All cells start out life with DNA In eukaryotic cells, DNA is contained within the nucleus

8 Constraints on Cell Size Cell size is limited by a physical relationship called the surface-to-volume ratio The volume of an object increases with the cube of the diameter The surface area increases with the square When a cell expands in diameter, its volume increases faster than its surface area does

9 Constraints on Cell Size (cont d.)

10 Constraints on Cell Size (cont d.) Surface-to-volume limits affect the form of colonial types and multicelled types Examples: Strandlike algae cells attach end to end Muscle cells are long and thin

11 Constraints on Cell Size (cont d.)

12 4.2 How Do We See Cells? Most cells are micrometers in diameter About fifty times smaller than the unaided human eye can perceive Microscopes are used to observe objects in the micrometer range of size

13 How Do We See Cells? (cont d.) electron microscopes light microscopes small molecules molecules of life viruses mitochondria, most chloroplasts bacteria carbohydrates DNA lipids proteins most eukaryotic cells 0.1 nm 1 nm 10 nm 100 nm 1 μm 10 μm

14 How Do We See Cells? (cont d.) human eye (no microscope) frog eggs small animals largest organisms 100 μm 1 mm 1 cm 10 cm 1 m 10 m 100 μm

15 How Do We See Cells? (cont d.)

16 How Do We See Cells? (cont d.) Light microscopes use visible light to illuminate samples Curved lenses inside the microscope focus light into a magnified image Researchers use stains or light-emitting tracers to see the details inside cells Electron microscopes use magnetic fields to focus a beam of electrons onto a sample

17 How Do We See Cells? (cont d.) A D B E C

18 4.3 What Is a Membrane? The plasma membrane s function is not limited to physically separating a cell s external environment from its internal one Other functions include regulating the crossing of substances into and out of cells

19 The Fluid Mosaic Model Several molecules are embedded within or attached to the lipid bilayer: Cholesterol, proteins, glycoproteins, glycolipids Fluid mosaic: model of a cell membrane as a two-dimensional fluid of mixed composition

20 The Fluid Mosaic Model (cont d.) one layer of lipids one layer of lipids

21 Proteins Add Function Many types of proteins are associated with a cell membrane Adhesion proteins: helps cells stick together Recognition proteins: identifies self cells Receptor proteins: triggers a change in cell activity Transport proteins: assists the movement of ions or molecules across the membrane

22 Proteins Add Function (cont d.) B C D E Extracellular Fluid Lipid Bilayer Cytoplasm

23 4.4 How Are Bacteria and Archaea Alike? All bacteria and archaea are single-celled organisms Archaea and bacteria were once formally grouped together as prokaryotes Archaea are more closely related to eukaryotes than to bacteria Archaea now have their own separate domain

24 How Are Bacteria and Archaea Alike? (cont d.) A C B D

25 How Are Bacteria and Archaea Alike? (cont d.) Structural similarities between bacteria and archaea: Protein filaments reinforce cell shape Numerous ribosomes for protein synthesis Cytoplasm contains plasmids (small circular DNAs) DNA is concentrated in a nucleoid

26 How Are Bacteria and Archaea Alike? (cont d.) Structural similarities between bacteria and archaea: (cont d.) Rigid cell wall surrounds the plasma membrane Polysaccharides form a slime layer or capsule around cell wall Pili (protein filaments) project from the surface Long, slender cellular structures called flagella are used for motion

27 How Are Bacteria and Archaea Alike? (cont d.) 1 cytoplasm, with ribosomes DNA in nucleoid plasma membrane cell wall capsule pilus 7 bacterial flagellum

28 Biofilms Bacterial cells often share a layer of secreted polysaccharides and proteins Biofilm: community of microorganisms living within a shared mass of secreted slime A biofilm is often attached to a solid surface, and may include: Bacteria, algae, fungi, protists, and/or archaea

29 Biofilms (cont d.)

30 4.5 What Do Eukaryotic Cells Have in Common?

31 What Do Eukaryotic Cells Have in Common? (cont d.) endoplasmic reticulum nucleus mitochondrion cell wall Golgi body vacuole An animal cell (a white blood cell of a guinea pig) A plant cell (from a root of thale cress)

32 The Nucleus The nucleus protects DNA from the metabolic processes of the cell Nuclear envelope: outer boundary of the nucleus; controls access to DNA Nucleoplasm: viscous fluid enclosed by the nuclear envelope Nucleolus: dense, irregularly shaped region where ribosomal subunits are assembled

33 The Nucleus (cont d.)

34 The Nucleus (cont d.) nuclear envelope nuclear pore nucleolus nucleoplasm DNA

35 The Nucleus (cont d.) nuclear pore nuclear envelope cytoplasm

36 4.6 What Is the Endomembrane System? Endomembrane system Series of interacting organelles between nucleus and plasma membrane Endoplasmic reticulum, Golgi bodies, and vesicles Produces lipids and proteins

37 What Is the Endomembrane System? (cont d.) central vacuole rough ER smooth ER Golgi body vesicle

38 A Variety of Vesicles Vesicle: small, membrane-enclosed organelle Functions: Transports substances Collects and disposes of waste, debris, or toxins

39 A Variety of Vesicles (cont d.) Peroxisome: breaks down amino acids, fatty acids, and toxic substances Lysosome: breaks down cellular wastes and debris Vacuoles: fluid filled; isolates or disposes of waste, debris, or toxic materials Central vacuole: fluid-filled vesicle in many plant cells

40 A Variety of Vesicles (cont d.)

41 Endoplasmic Reticulum Endoplasmic reticulum (ER): A continuous system of sacs and tubes extending from the nuclear envelope Smooth ER: makes lipids and breaks down carbohydrates and fatty acids Rough ER: ribosomes on the surface synthesize proteins

42 Golgi Bodies Golgi body: Modifies proteins Packages the finished products into vesicles Some of the vesicles deliver their cargo to the plasma membrane; others become lysosomes

43 What Is the Endomembrane System? (cont d.) nuclear envelope vesicle rough ER new protein 1 2 Vesicles Rough ER

44 What Is the Endomembrane System? (cont d.) smooth ER Golgi body plasma membrane 3 4 Smooth ER Golgi Body

45 4.7 What Do Mitochondria Do? Mitochondrion: double-membraned organelle that produces ATP by aerobic respiration in eukaryotes Nearly all eukaryotic cells (including plant cells) have mitochondria The number varies by the type of cell and by the organism

46 What Do Mitochondria Do? (cont d.) mitochondrion

47 What Do Mitochondria Do? (cont d.) outer membrane inner membrane outer compartment inner compartment A B

48 4.8 What Are Plastids? Plastids: double-membraned organelles that function in photosynthesis, storage, or pigmentation in plant and algal cells Examples: chloroplasts, chromoplasts, amyloplasts Chloroplasts: specialized plastid for photosynthesis in some protists and plant cells

49 What Are Plastids? (cont d.) chloroplast

50 What Are Plastids? (cont d.) A B two outer membranes stoma inner membrane

51 What Are Plastids? (cont d.)

52 4.9 What Is a Cytoskeleton? Cytoskeleton: Network of interconnected protein filaments Supports, organizes, and moves eukaryotic cells and their parts

53 What Is a Cytoskeleton? (cont d.) Microtubules: hollow filament of tubulin subunits Involved in movement Microfilaments: fiber of actin subunits Reinforces membranes; involved in muscle contractions Intermediate filament: stable cytoskeletal element Structurally supports membranes and tissues

54 What Is a Cytoskeleton? (cont d.) tubulin subunit actin subunit dimer tetramer sheet of tetramers coiled sheet D A Microtubule B Microfilament C Intermediate filament

55 What Is a Cytoskeleton? (cont d.) Motor proteins Associate with cytoskeletal elements Move cell parts when energized by a phosphate-group transfer from ATP Drag cellular cargo along tracks of microtubules and microfilaments

56 What Is a Cytoskeleton? (cont d.)

57 What Is a Cytoskeleton? (cont d.) Flagella: propel cells Cilia: short, movable structures that project from the plasma membrane Centriole: barrel-shaped organelle from which microtubules grow Basal body: develops from a centriole Pseudopod: temporary protrusion; facilitates movement and engulfs prey

58 What Is a Cytoskeleton? (cont d.) flagellum sperm

59 What Is a Cytoskeleton? (cont d.) pair of microtubules dynein arm plasma membrane A

60 What Is a Cytoskeleton? (cont d.) B basal body

61 What Is a Cytoskeleton? (cont d.) C

62 4.10 What Structures Form on the Outside of Eukaryotic Cells? Cell matrixes Extracellular matrix: complex mixture of cell secretions Primary wall: first cell wall of young plant cells Secondary wall: lignin-reinforced wall that forms inside the primary wall of a plant cell Lignin: stiffens cell walls of vascular plants

63 What Structures Form on the Outside of Eukaryotic Cells? (cont d.) plasma membrane primary wall cytoplasm A middle lamella

64 What Structures Form on the Outside of Eukaryotic Cells? (cont d.) secondary wall primary wall B

65 What Structures Form on the Outside of Eukaryotic Cells? (cont d.) ER cytoplasm plasma membrane cell wall C

66 What Structures Form on the Outside of Eukaryotic Cells? (cont d.) Cell matrixes (cont d.) Cuticle: secreted covering at a body surface In plants, a cuticle of waxes and proteins helps stems and leaves fend off insects and retain water

67 What Structures Form on the Outside of Eukaryotic Cells? (cont d.) cuticle outer cell of leaf photosynthetic cell inside leaf

68 Cell Junctions Cell junction: connects a cell to another cell or to an extracellular matrix Tight junction: adhesion proteins that join epithelial cells Prevents fluids from leaking between cells

69 Cell Junctions (cont d.) free surface of epithelial tissue tight junctions gap junction B adhering junction basement membrane A

70 Cell Junctions (cont d.) Adhering junctions: connect to cytoskeletal elements Fastens cells to each other and basement membrane Gap junctions: closeable channels formed across the plasma membranes of adjoining animal cells Plasmodesmata: open channel formed between the cytoplasm of adjacent plant cells

71 4.11 What Is Life? Life is a long list of properties that collectively describe living things 1. Make and use the organic molecules of life 2. Consist of one or more cells 3. Engage in self-sustaining biological processes (e.g., metabolism and homeostasis) 4. Change over their lifetime (e.g., growing, maturing, and aging)

72 What Is Life? (cont d.) Life is a long list of properties that collectively describe living things (cont d.) 5. Use DNA as their hereditary material when they reproduce 6. Capacity to change over successive generations (e.g., adapting to environmental pressures)

73 4.12 Application: Food for Thought Strains of E. coli that are toxic to people live in the intestines of other animals Humans are exposed when they come into contact with feces of animals that harbor it Example: eating contaminated ground beef or contaminated fresh fruits and vegetables Food workers are working to reduce the number and scope of harmful E. coli outbreaks

74 Application: Food for Thought (cont d.)